中文摘要：

对于描述正交金属板材屈服和塑性变形行为而言，Hosford比Hill屈服函数更具有适应性．但Hos—ford屈服函数要求三个主应力方向与板材的轧制方向（RD）、横向（TD）和法向（ND）一致，导致其使用不便．因此论文引入方向函数，将方向函数泰勒展开到方向的六次项，提出新的包含主应力方向效应的广义Hosford正交金属材料屈服函数．当η=2时，广义Hosford屈服函数可退化成Hill屈服函数．实验证明，利用包含主应力方向效应的Hosford正交材料屈服函数计算出的q值、r值和屈服应力与实验结果都高度吻合．此屈服函数包含11个参数，形式较简便，更具一般性，为研究金属材料的力学性能奠定了理论基础．

英文摘要：

Although the Hosford yield function is more suitable for describing both the yielding and the plastic deformation of orthorhombic materials than the Hill quadratic yield function, it suffers from the restriction that the three principal stresses have to be coaxial with the pressing direction （RD）, transversal direction （TD） and vertical direction （ND） for metal sheets. Hence, this article derives the Hosford yield function for orthorhombic materials with the direction of principle stress taken into account by the six-or- der plastic tensors obtained via the Taylor expansions of an introduced orientation-dependent function. And when η=2, this yield function can be reduced to the Hill quadratic yield function. Finally, it shows that the q-value, r-value and yield stress obtained from the Hosford yield function for orthorhombic materials considering the principle stress direction agree well with the experimental results. This yield function only requires 11 material parameters, and possesses the merits such as simple form, generality, and so on. It can lay a theoretical foundation for analyzing the mechanical properties of metal materials.